One thing is worse than a low response rate to an email campaign - a rise in the number of recipients who unsubscribe. The arrival of every alert relaying the news of another lost customer hurts.

"What did I say?" you may ask.

Quite. And remember that a subscriber who does not feel that they signed up or is sick of your newsletter may just screen it out like old crud sent by Grum, the recently dismantled spam botnet.So you might be bleeding more readers than you think.

Keeping subscribers interested is tough. According to research conducted by the marketing firm Exact Target, 91 per cent of users change their mind about newsletter subscriptions after committing.

"If you think of a consumer's online interaction with your brand as a treasured relationship - and you should! - the next logical step is to explore the termination of that relationship, or what we've dubbed:The Social Break-Up," the company says.

Here's some insight into why subscribers dump you.

1. Your content is irrelevant

One key reason that recipients unsubscribe is that the email is "off-topic". That is, it contains information that the recipient would not expect or did not sign up for, says the director of the marketing firm Smile Media, Liz Van Dort.

2. You sound like a used car dealer

If your marketing message shouts "buy now cheap" or uses "blatantly sell-focused language, that tends to annoy people greatly", says Van Dort, who regularly runs email marketing campaigns.

"People want to be seduced or intrigued into buying - not told to buy," she adds.

3. You are offensive

Off-colour content that is "loaded or divisive" will also lose you subscribers, Van Dort says. Beware anything controversial.

"Stay away from sex, race, religion or politics." Avoid causing offence.

4. You are not mobile-friendly

In the last two years, a shift has happened - many of us now read emails on a mobile device, Van Dort says.

So if your message is not mobile-enabled or reads badly on a mobile, recipients who browse their email that way will switch off and unsubscribe.

5. You do not mix it up

Remember that even regular clients soon tire of emails just listing products and prices, Van Dort says.

Reduce the client's inclination to unsubscribe by, say, inserting a relevant article or "back story" and embedding eye-catching imagery, she says.

6. You ramble

We live in an instant, want-it-now society, says business mentor Geoff Golding.

"Most emails are too verbose in their message. People don't as a general rule read large quantities of text," Golding says. Keep it concise, he adds.

7. You make false connections

Emails get treated as junk when they make easy assumptions about the reader's interests.

For instance, Golding says, just because he bought some tea towels on the internet for his wife, that does not mean he wants "incessant"emails about linen from the shop in question, which he has blocked.

8. You have no unsubscribe button

The biggest no-no is not to have an unsubscribe function or - worse still - make it tricky to unsubscribe, Golding says. That means you are junk-mailing, he adds and explains the result - recipients effectively stop their subscriptions through flagging you as spam.

9. You pester subscribers

The daily or weekly recurrence of marketing messages gets annoying, says Golding.

In fact, he says, bombardment "invites" recipients to unsubscribe.

Avoid sending a mail-out more than once every 75 days, he advises. Then, instead of causing annoyance, the contact will "kickstart" the customer's memory of your business.

10. You are boring

The cardinal sin of email promotion, marketers agree, is blandness.Make your message crisply compellingly - spice it up with an offer, say. Or skip sending the email altogether.

- Sydney Morning Herald